The use of motorized treadmills has become increasingly popular for fitness as well as for various therapeutic purposes. In a typical motorized treadmill, an endless belt travels around two parallel and spaced apart cylindrical rollers, with at least one roller being directly driven by the motor. A support deck located beneath the endless belt supports the belt and the user when the treadmill is in operation. Further, known treadmills have either no support bars, or more typically, have rigid support bars or handrails positioned on either side of the belt to provide a balancing aid for the user. An additional feature of many treadmills today is an elevation system that enables the user to increase the incline of the treadmill, thereby increasing the exercise difficulty level.
The motor that drives the treadmill typically has a flywheel mounted on the motor shaft for improving the rotational motion of the belt. Under normal use, a greater load is imposed on the motor during those times that the user is stepping down on the belt, as opposed to when the user is not stepping down, such as during the brief periods between steps. Stepping down slows down the motor and may lead to a jerky movement of the belt that is noticeable to the user. The flywheel is an additional mass that is rotating with the motor shaft, therefore providing additional inertial forces that counteract the tendency of the motor to slow down each time the user's foot contacts the belt. Because the flywheel is mounted on the motor shaft, however, it creates an overhang load on the motor shaft. This imposes an additional load on the motor bearings and reduces the life of the motor, and also imposes an additional load on the electronics and power supplies that govern operation of the treadmill. In addition to the overhang load, the motor also experiences significant unidirectional loading from driving the treadmill rollers. Since the life of a motor is related to the loads imposed on it, the need exists for a motorized treadmill in which these loads are substantially reduced. Further, it would be desirable to provide a treadmill having a flywheel assembly that further improves the fluid rotational motion of the belt.
As indicated above, many treadmills also include an elevation system. One existing type of elevation systems consists of a single motor and gear unit, such as a single motor mounted in the front center region of the treadmill that drives a linear actuator to lift up the front end of the treadmill. Such a system is typically mounted on the treadmill at only two points, one on either side of the motor and gear unit, and therefore tends to wobble under use. Further, the single motor and gear unit provides only a limited lifting force. Another typical elevation system consists of a motor mounted in the front center region of the treadmill that simultaneously drives two linear actuators that are mounted in the front right and front left corner regions of the treadmill. Although this type of system improves the stability of the treadmill and provides additional lifting power, the two linear actuators must be driven in synchrony by the motor to lift the treadmill belt in a level manner. In operation, such synchrony is difficult to achieve, and if one of the linear actuators fails to function properly the entire elevation system may bind up and cease to function, making periodic cleaning and maintenance necessary. Accordingly, a need exists for a treadmill elevation system that provides sufficient lifting power and stability, and that is not subject to the limitations described above.
Another area for improvement in treadmill design involves providing a more comfortable running or walking plane that will dampen or cushion the impact of the force exerted on the deck by a user. A suspended deck is a widely used dampening system. Dampening mechanisms thus far, however, have been unable to provide a dampening system that will account for the vast differences in weight of treadmill users. This aspect is particularly important for treadmills that are used by the general public, such as those in fitness clubs. For example, many types of suspended decks will comfortably dampen the stepping force of a 180 or 200 pound person, but will not provide sufficient dampening for a 100 or 110 pound person. Therefore, a need exists to provide an improved dampening system that is simple in construction, and that will automatically provide dampening for users in all weight ranges.
Finally, as indicated above, most treadmills include rigidly attached handrails mounted on either side of the belt to assist in balancing the user. These devices are particularly useful for beginners, older users, users with disabilities, or simply users who prefer to have a balancing aid readily available. Many users, however, are experienced and do not use these handrails, and many would prefer to simultaneously exercise their arms, e.g., by using free weights or the like. The latter is difficult with treadmills having rigidly attached handrails, since they cannot easily be moved out of the way. Accordingly, it would be desirable to provide a treadmill that includes retractable handrails that are available to those who desire to use them, and that are readily retractable for those who do not.